Turbo charging or supercharging the intake air into diesel engines is common place for better performance. The charging of the air provides for greater initial density of the air and thus more air for a more powerful combustion cycle. The intake air may, however, be excessively heated during the charging process. Consequently, charge air coolers are common in diesel engines for taking excess heat out of the intake air to prevent premature compression ignition.
Excess cooling of the charged fresh air provides opportunities for condensation to occur in the intake system. The condensation becomes a more serious issue in diesel engines that utilize exhaust gas recirculation. Exhaust gas recirculation is commonly used to reduce engine emissions into the atmosphere. Due to the high sulfur content of diesel fuel, the re-introduction of the exhaust gasses into the cooled intake air provides for condensation of the sulfur in the form of sulfuric acid. The condensation and formation of sulfuric acid has a corrosive effect on the intake system. If the sulfuric acid is introduced into the engine, it can detrimentally act on the cylinder walls and piston rings and produce overall increased engine wear.
While proposed solutions have included the reduction of the amount of sulfur in diesel fuel, use of special corrosive-resistant materials, these solutions are expensive. One other solution is to prevent the condensation of the EGR gasses in the first place to prevent the formation of the sulfuric acid. Previous attempts at preventing condensation have incorporated air dryers to take the moisture out of the intake air before mixing with the EGR gasses which adds considerable expense to the engine.
Other systems provide a bypass of the charge air cooler by bypassing the turbocharger completely. As such, the bypass degrades the efficiency of the turbocharger system by introducing non-charged air into the intake system. Other systems provide completely separate EGR gas conduits which increase the conduit needed for the intake system.
What is needed is charge air intake system that proportions the intake air between the charge air cooler and a bypass duct for maintaining the temperature of the intake air above its dew point to allow introduction of EGR gasses without condensation in an efficient intake passage layout.